1. Field of the Invention
The present invention generally relates to plastic product metallization, in particular to a novel method of preparing a double-layer antimicrobial coating.
2. Description of Related Art
Since the beginning of the 21st century, plastic products have become an indispensable part of our daily lives as many objects of daily use are made of some kind of plastic. For example, plastic products are used extensively in various electrical appliances (such as telephones, washing machines, computers, and electric switches). With environmental pollution, the plastic products of daily use carry a large quantity of bacteria on the surface of the plastic products and have become a bacterial pollution source or an infection source. Statistics show that approximately 17 million people die each year due to infectious diseases. Therefore, the research and development of novel coating products with the antimicrobial function is significantly important to the issues of improving our living environment, reducing the incidence of diseases, and protecting our health.
Since the global spread of SARS virus in 2003 to the most recent outbreak of H1N1 influenza worldwide, consumers have more concerns about food safety and various pathogens existing in our environment. Antimicrobial agents are used more extensively in the application of plastics than ever to meet the requirements of public health and daily living, and the annual growth rate of antimicrobial agents used in plastics is approximately equal to 3.5%˜4%. North America is the world's top user of antimicrobial agents (including biological inhibitors) and consumes approximately 40% of the world total, while Japan consumes 20% of the world total. Japanese has the largest consumption of antimicrobial agents per capita, much greater than North Americans and Europeans. According to a recent survey by the world-renowned public opinion research company Gallup poll, a vast majority of consumers said they are willing to buy antimicrobial products and 75% of the consumers have a preference for antimicrobial products. In the survey, over 7 out of 10 persons revealed that they have used more than six types of antimicrobial products. Consumers generally believe that it is necessary to use the antimicrobial products for different applications and environments.
As disclosed in P.R.C. Pat. No. ZL200420071581, a substrate of an antimicrobial product with an abrasion resistant surface is made of metal, inorganic, or polymer materials, and the surface of such product is coated with a silver, copper, or silver-copper complex film by physical vapor deposition (PVD). However, the coating of the product produced in accordance with this patented technology still has the drawbacks of insufficient abrasion resistance and low sustainability effect.